1. Field of the Invention
This invention relates to an oil-cooled compressor having a suction control valve in a suction passage formed in a compressor body, and a discharge valve in a discharge passage.
2. Description of the Related Art
An oil-cooled compressor designed to compress an air with a lubricating oil cooled for the purpose of cooling a compressed air and sealing a clearance in a compression space has been widely known. This type of compressor is the same as other types of compressors in the respect that the supply of lubricating oil to each part of rotor shaft bearings and shaft seal sections is required for lubrication to bearings of a shaft of a rotor for air compression, and for prevention of air leakage at shaft seal sections. To each of these sections the lubricating oil is supplied separately.
In the aforementioned oil-cooled compressor, a rotor shaft is installed with at least one of its end sections, four example four end sections in the case of a screw compressor, mounted through a casing of the compressor body in order to receive a driving power from a motor. Between this section of the rotor shaft and the casing is provided a shaft seal section for sealing a clearance communicating with the outside.
To this shaft seal section, as described above, the lubricating oil is supplied separately from the compression space and the bearing sections. However, since the rotor shaft is a rotating part, the clearance between the rotor shaft and the shaft seal section can not be fully eliminated; there exists a slight clearance around the rotor shaft. The lubricating oil supplied to the shaft seal section will leak little by little through the clearance with the lapse of time. The oil, if left leaking, will, together with dust, soil the interior of a package containing the equipment and the floor. It, therefore, presents such a problem that installation of a discharge pipe will be required for discharging the leaking oil out of the equipment.
The discharge of the leaking oil, therefore, presents another problem that regular replenishment of lubricating oil circulating within the equipment will become necessary, thus requiring more manhours for equipment maintenance work. Furthermore the lubricating oil itself is improved in durability and accordingly becomes costly, hence causing an increase in running cost.